The invention provides the use of an optionally hydroxy-protected
4-hydroxyo or hydroperoxy-3,5-dioxopyrazolidine or an equivalent wherein a
pyrazolidine ring attached oxygen is replaced by a sulphur, or a
physiologically acceptable salt thereof, for the manufacture of a
medicament for use in therapy or prophylaxis. Additionally, the invention
provides a method of combating HIV infection which comprises administering
to an HIV-infected patient a T-lymphocyte growth suppressing agent,
preferably a pyrazolidinol, in an amount sufficient to suppress
T-lymphocyte growth in said patient for a period sufficient to reduce the
T-lymphocyte concentration in lymph nodes in said patient by at least 25%,
said administration being repeated at intervals of at least 3 months.
